On 9/30/2018 6:01 PM, Jan Ekström wrote:
> Sn Sun, Sep 30, 2018 at 8:56 PM <alx.sukha...@gmail.com> wrote:
>>
>> ...
>> + if (st->codecpar->codec_id == AV_CODEC_ID_H264) {
>> + if (pkt->size >= 5 && AV_RB32(pkt->data) != 0x0000001 &&
>> + (AV_RB24(pkt->data) != 0x000001 ||
>> + (st->codecpar->extradata_size > 0 &&
>> + st->codecpar->extradata[0] == 1)))
>> + ret = ff_stream_add_bitstream_filter(st, "h264_mp4toannexb",
>> NULL);
>> + } else if (st->codecpar->codec_id == AV_CODEC_ID_HEVC) {
>> + if (pkt->size >= 5 && AV_RB32(pkt->data) != 0x0000001 &&
>> + (AV_RB24(pkt->data) != 0x000001 ||
>> + (st->codecpar->extradata_size > 0 &&
>> + st->codecpar->extradata[0] == 1)))
>> + ret = ff_stream_add_bitstream_filter(st, "hevc_mp4toannexb",
>> NULL);
>
> Please verify that there is no AVCc/Annex B deciding helper function
> within lavf/lavc that could be used here. I tried to ask about this on
> IRC but didn't get responses so I can't straight up note you a
> function name. If there's none, then it might be worth making a lavf
> helper for that since I think at least movenc/matroskaenc try to
> figure out if the input bit stream is Annex B and convert it the other
> way.
The *_mp4toannexb bitstream filters convert mp4 encapsulated packets
into annex-b, or pass already annex-b formatted packets through.
Assuming ivf is meant to use annex-b, then what this patch is doing is
correct.
>
> Additionally, please make sure that the files created with these
> changes can be demuxed with the FFmpeg IVF demuxer (ivfdec.c). I would
> guess the H.264 stuff would work, but since the IVF demuxer utilizes
> the ff_codec_bmp_tags list, which doesn't seem to contain HEVC entries
> I would guess additional stuff would be required there.
>
> That of course doesn't have to be within this patch, but just within
> this patch set (one patch for demuxer, one for muxer).
Yes, a demuxer patch removing the usage of ff_codec_bmp_tags and
replacing it with a custom ivf specific one is needed after, or probably
before this patch.
>
> Best regards,
> Jan
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>
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